pcre_maketables man page
PCRE — Perl-compatible regular expressions
const unsigned char *pcre_maketables(void);
const unsigned char *pcre16_maketables(void);
const unsigned char *pcre32_maketables(void);
This function builds a set of character tables for character values less than 256. These can be passed to pcre[16|32]_compile() to override PCRE's internal, built-in tables (which were made by pcre[16|32]_maketables() when PCRE was compiled). You might want to do this if you are using a non-standard locale. The function yields a pointer to the tables.
There is a complete description of the PCRE native API in the pcreapi page and a description of the POSIX API in the pcreposix page.